<li><g:link controller="Listing" action="Index">All Listings</g:link> </li>
<g:if test="${session.user}">
    <li><g:link controller="Listing" action="myListings">My Listings</g:link></li>
    <li><g:link controller="Listing" action="create">Create a New Listing</g:link></li>
</g:if>